Fiber optic lighting systems are used in a variety of applications to provide a cool, flexible, safe source of light. The assignee of the present invention provides fiber optic light systems for use in signs, displays, swimming pools and general area lighting. One such fiber optic light system for providing multi-color light effects is described in U.S. Pat. No. 5,528,714 issued Jun. 18, 1996, to Kingstone et al., assigned to the assignee of the present invention and incorporated by reference herein. A fiber optic lighting system may typically include a light source and a fiber optic cable bundle for transmitting light from the light source to a location remote from the light source. The light source may typically include an enclosure containing a light bulb, a means for securing the end of a fiber optic cable bundle near the light bulb, a power supply or other electronic equipment, and a fan for providing cooling air to the enclosure.
One of the limiting characteristics of a fiber optic light system is the amount of light that can be produce from such systems. Numerous advances have been made to improve the optical performance of the fiber optic cables in order to reduce the losses in the system. For example, U.S. Pat. No. 5,333,228 issued Jul. 26, 1994, to Kingstone, assigned to the assignee of the present invention and incorporated by reference herein, describes a fiber optic cable having a reflective center core for reflecting inwardly directed emissions back outwardly.
It is known to increase the amount of light introduced at the inlet end of the fiber optic cable bundle in order to increase the amount of light produced by the system. However, light bulbs used to produce such light, for example incandescent and halogen lamps, produce a significant amount of heat energy along with the visible light energy. As the power of the light bulb is increased and as the bulb is placed closer to the ends of the fiber optic cables, it becomes increasingly difficult to provide cooling for the cable ends. It is known that plastic cable fibers will melt at approximately 125 degrees Centigrade. However, local melting of the cable will cause a depression in the cable end wherein cooling air becomes stagnant and local heating will intensify. Even a small local hot spot will quickly destroy the functionality of a cable fiber. Therefore, it is necessary to provide an additional margin of safety against melting. U.S. Pat. No. 5,838,860 issued Nov. 17, 1998, to Kingstone et al., assigned to the assignee of the present invention and incorporated by reference herein, describes the use of a plate of heat absorbing material as part of a temperature control scheme within the enclosure of a fiber optic illumination system. In many designs the factor limiting the brightness that can be achieved in the cable is the cooling of the cable ends.
In a light source for a fiber optic system it is necessary to provide local cooling to the end of the cable bundle fibers as well as general cooling for the bulb and other components included in the light source enclosure. The heat generated by the bulb and other electronics within the enclosure necessitates the supply of a high volume of cooling air. However, for cooling the cable end the volume of air is not as critical as the velocity of the air, as a result of the geometry of the cable end and the relatively poor thermal conductivity of the air. In order to provide the required velocity for cooling the fiber end, prior art systems have used fans that are much larger than necessary for the general cooling requirements. As a result, such fans have proven to be noisy and have consumed more electrical power than is necessary for the overall application requirements. Alternatively, two air moving devices have been used in a single light source; a fan for general cooling and a blower to provide a source of high velocity cooling air for the cable ends.
Furthermore, prior art fiber optic cable systems incorporating the higher light output of metal halide lamps have been limited. Although these lamps produce more visible light than incandescent and halogen lamps, they also produce more infrared and ultraviolet energy, thereby making it more difficult to provide the necessary cooling to the fiber ends in order to take advantage of these higher output lamps.
What is necessary is an improved cooling arrangement for a fiber optic lighting system. Therefore, it is an object of this invention to provide a cooling arrangement for a fiber optic light source that provides adequate cooling for the cable end without providing excess general cooling. It is a further object of this invention to provide a fiber optic light source that incorporates a metal halide light bulb without the danger of melting of the fiber optic cable bundle ends. It is a further object of this invention to provide a more efficient and more quiet cooling arrangement for a fiber optic cable light source.